1. Field of the Invention
The present invention relates to an image forming apparatus and, more particularly, to an alignment device for a developing roller and a squeegee roller of an image forming apparatus in which the developing roller and the squeegee roller can be precisely aligned with respective backup rollers.
2. Description of the Related Art
In general, an image forming apparatus which reproduces text and images on a recording medium according to transmitted image data signals is provided with a photosensitive member such as a photosensitive drum or a photosensitive belt for forming a latent electrostatic image thereon, a charging device for charging the surface of the photosensitive member, an exposure device for forming a latent electrostatic image of a predetermined pattern by illuminating the charged surface of the photosensitive member by a light beam, a developing device for developing the latent electrostatic image by applying a developing agent such as a developer liquid or a toner to the exposed latent electrostatic image, and a transfer device for transferring the developed image to a recording medium.
FIG. 1 shows a schematic diagram illustrating the structure of a conventional image forming apparatus.
Referring to FIG. 1, the image forming apparatus comprises a photosensitive belt 104 mounted about first, second and third belt rollers 101, 102 and 103 to circulate about them, a discharging device 105 for erasing any remaining charge on the photosensitive belt 104, and a charging device 106 for charging the surface of the photosensitive belt 104. Exposure devices 107, 108, 109 and 110 having respective laser scanning units (not shown) are provided for illuminating an imaging region of the charged photosensitive belt 104 to selectively erase charges in the shape of an image by respective laser beams in order to form a latent electrostatic image. Developing devices 111, 112, 113 and 114 are provided for developing the latent electrostatic image by applying developer liquid according to corresponding colors, i.e., Y (yellow), M (magenta), C (cyan) and K (black). A drying device 115 for drying developer liquid applied to the latent image, and a transfer device 116 for transferring an image developed on the photosensitive belt 104 to a recording medium 117, such as a paper sheet or a film frame, are also provided.
In this case, the developing device 111 comprises a developing roller 111a for applying the developer liquid to the photosensitive belt 104, a developer liquid supplying device 111b for supplying the developer liquid to the developing roller 111a, a cleaning roller 111c for removing the developer liquid adhering to the rear surface portion of the developing roller 111a, first and second squeegee rollers 111d and 111e for removing excess developer liquid from the photosensitive belt 104, first and second blades 111f and 111g for removing the developer liquid adhering to the first and second squeegee rollers 111d and 111e, and a developer liquid recovery container 111h for recovering the developer liquid within the apparatus. In addition, the drying device 115 is provided with a heating roller 115h for drying the developer liquid adhering to the photosensitive belt 104, and auxiliary rollers 115r and 115s for removing the liquid toner remaining on the heating roller 115h, and the transfer device 116 comprises a transfer roller 116t for transferring an image from the photosensitive belt 104 to the recording paper 117 by relatively rotating in contact with the first belt roller 101 with the photosensitive belt 104 interposed therebetween, and a pressure roller 116p for fixing the image transferred on the transfer roller 116t onto the recording paper 117 by relatively rotating in contact with the transfer roller 116t with the recording paper 117 interposed therebetween.
In the above conventional image forming apparatus, when the developing roller 111a and the squeegee roller 111d contact the photosensitive belt 104 to perform their respective functions, the developing roller 111a and the squeegee roller 111d are respectively provided with backup rollers 201 and 202 for effectively performing their functions, as shown in FIG. 2.
However, since the shafts 201s and 202s of the backup rollers 201 and 202 are supported by supporting blocks 201b and 202b respectively provided with a U-shaped groove and a V-shaped groove, and the supporting blocks 201b and 202b are respectively assembled to frames 203 and 204 of the squeegee roller 111d and the developing roller 111a, as shown in FIG. 2, it is not easy precisely to align the developing roller 111a and the squeegee roller 111d with the respective backup rollers 202 and 201 due to assembly tolerances or the like. That is, vertical alignment of the squeegee roller 111d with the backup roller 201, vertical alignment of the developing roller 111a with the backup roller 202, and the maintaining of predetermined gaps between the corresponding rollers are not easy. Accordingly, it is difficult precisely to adjust the distance between the centers of the U-shaped supporting block 201b and V-shaped supporting block 202b.